Meg Cabot’s The Princess Diaries enjoyed enough success when it first came out that it didn’t take long (less than a year, actually) for a movie to come out using the same name and basic concept.
But there are actually a lot of huge differences between The Princess Diaries books and the movies. Do you know them all? If you haven’t finished reading all the books in the series, be warned: there are spoilers ahead!

The Princess Diaries movie takes place in San Francisco, not New York.
Director Garry Marshall wanted to be near his daughter and son-in-law, along with their grandkids. He said that “New York’s a hard shoot, and I didn’t want to go to Toronto, which is the fake New York. It’s the fake everything” (LaSalle, 2001).

Mia’s father is not dead in the books.
In the books, Mia’s father –the Crown Prince of Genovia– is alive and well… but he has testicular cancer, and so can’t have any more children. Thus, his daughter Mia is tapped as the next heir, and she must take “Princess Lessons” from her grandmother, the Dowager Princess of Genovia.
In contrast, the Disney movies thought testicular cancer might be too sensitive of a subject for a G-rated movie, so they just killed the Crown Prince off altogether. In many ways, this alters how the movie progresses, including Mia’s character.
Interestingly enough, Anne Hathaway’s father, Gerald Hathaway (a lawyer and not an actor) “played” Prince Phillipe in the movies; it was his picture on Mia’s table, and in the scene fishing when Mia read his letter to her.

Grandmère and Mia (mostly) get along in the movies.
It’s hard to imagine famed actress Julie Andrews playing a chain-smoking, alcoholic, poodle-stroking, overbearing Dowager Princess, which would have been her role had Garry Marshall not adapted the role of Mia’s paternal grandmother specifically for Julie Andrews. Of course, Andrews’ Grandmère is still strict when it comes to training Mia to be a princess, but not anywhere as manipulative as the original character in the books.
In fact, in later books in The Princess Diaries series, Mia comments on how ridiculous it is that her movie counterpart gets along with “Grandmère” so well.
Mia’s mother dating the algebra teacher is actually a big deal.
In the books, the romance that starts in the first book continues all the way through the tenth book of the series, and results in a half-brother for Mia, Rocky (her half-brother in the movie is named Trevor). In the eleventh book, Royal Wedding, a “news article” at the beginning of the book indicates that Mr. Gianini died recently from congestive heart failure, leaving Helen Thermopolis a widow. Mia founded a community center for children in New York City in her stepfather’s honor, aimed at helping children and teens “acquire the skills they need to succeed in school or their chosen future career path.”
Helen and Frank’s romance is not nearly as big of a deal in the movies, where Mia struggles more with keeping her status as a princess secret from her classmates, preparing for the Genovian Independence Day Ball, and dealing with her secret crush on her best friend’s brother.

The romance between the Dowager Queen and Mia’s bodyguard was not part of the original story.
At the start of the first movie, the Dowager Queen Clarisse Renaldi (her name in the books is slightly different; it’s Dowager Princess Clarisse Marie Grimaldi Renaldo) recently lost her husband, King Rupert (his name was Artur in the books). She is constantly seen wearing black, up until a scene where she dances with Mia’s bodyguard (and her former Head of Security), Joe. He encourages her to move on by saying she wears too much black, and after that scene, the Dowager Queen starts to integrate more color into her wardrobe.
She gradually acknowledges her feelings for Joe, Mia’s bodyguard (and her Head of Security), to the point where they actually get married in Princess Diaries 2: A Royal Engagement. The inclusion of this romance was actually at the insistence of the actors, Julie Andrews and Hector Elizondo, who wanted a romance for people over fifty years old featured in the movie.
However, the character Joe doesn’t exist in the books; instead, Mia’s bodyguard is a man named Lars van der Hooten. Additionally, in the books, Mia’s Grandpère died in 1978, long before Mia was born. If Clarisse spent any significant time mourning him, she did it before the events of the books, as she has no compunction wearing colors (especially purple) in the books.

Mia has “short, mousy brown hair” with blonde highlights in the books, not chestnut brown hair.
Actress Anne Hathaway had her film debut playing clumsy, geeky Princess Mia in The Princess Diaries movie. A combination of factors went into her casting, including directory Garry Marshall’s granddaughters saying that she had the most “princess hair” of all the ladies whose audition tapes they watched.
Many of the book covers attempt to illustrate what Mia looks like, and in many of them, her hair is blonde. Sometimes it is short and straight, while other times it is frizzy or curly (especially on the French covers). The German editions often feature a redheaded Mia, while other avoid illustrating Mia altogether and instead use a combination of tiaras, scepters, and other jewelry to tie in the “royal” themes of the books.

Fat Louie is an orange cat in the books, not a black and white cat.
Mia often talks about her orange and white cat Louie in the books, and how she got him when she was six years old in exchange for stopping the bad habit she had of sucking her thumb.
Most orange and white cats (called “gingers”) are male due to the gene controlling fur color being on the male chromosome, but there are some rare instances of female ginger cats.
Multiple cats played Mia’s fat feline in The Princess Diaries depending on the needs of the shot: whether the cat needed to be sitting, held by an actor, jump for a scene, or, in the concluding shot of the movie, sit on an envelope with the motto of Genovia on it.
Black and white cats are often called “tuxedo” cats.
Mia is actually fourteen in the first book, not sixteen.
Mia’s mother Helen claims that she and Mia’s father planned to tell Mia about being a princess when she turned eighteen years old. However, the letter from Mia’s father in the movies indicates it was to be given to her on her 16th birthday, and his death didn’t seem to expedite the situation all that much.
In the books, since Mia’s father is not dead at all, it is actually his cancer diagnosis that prompts the revelation that Mia is actually the heir to the Genovian throne, rather than any particular birthday of Mia’s.
Many of the books take place over the course of a a few weeks during a single school semester, which means that Mia doesn’t actually turn fifteen years old until Vol. 5 (her birthday is May 1st), Princess in Pink, or enter the ninth grade until Vol. 6, Princess in Training. Therefore the timeline is something like this:
- Volume 1: Princess Diaries — September 23, 2000 – October 19
- Mia is stated to be 14 years old in this book
- Volume 2: Princess in the Spotlight — October 20 – November 1
- Volume 3: Princess in Love — early December – December 20
- Volume 4: Princess in Waiting — January 1, 2001 – January 23
- Volume 4.5: Project Princess — March 10 – March 16
- Volume 5: Princess in Pink — April 30 – May 11
- Mia turns 15 years old during this book
- Volume 6: Princess in Training — September 7 – 14
- Volume 6.5: The Princess Present — December 22 – 25
- Volume 7: Party Princess — March 2 – 10, 2002
- Volume 7.5: Sweet Sixteen Princess — April 28 – May 1
- Mia turns 16 during this book)
- Volume 7.75: Valentine Princess — June 5
- The events recounted in the journal Mia finds on June 5 actually take place between Vols. 4 and 4.5, from February 11 – 14, 2001
- Volume 8: Princess on the Brink — September 7 – 10
- Mia’s junior year in high school
- Volume 9: Princess Mia — September 10 – ??
- Volume 10: Forever Princess — April 27, 2003 – May 7
- Mia’s senior year in high school
- Mia turns 18 during this book
- Volume 11: Royal Wedding — April 28, 20?? – June 20
- Mia’s college graduation is stated to be five years before the events of this book, but it is not known whether Mia took a gap year or graduated within the “standard” four years or not
- Mia’s age is stated to be 25-26 during this book, meaning she graduated at age 20-21, so (assuming she started college immediately after high school and graduated within four years) the timeline would place her college graduation in 2008, and not in 2010 (based on the book’s publication date in 2015)

Mia has more friends than just Lilly Moscovitz
Many of Mia’s friends, including Tina Hakim Baba, Boris Pelkowski, Shameeka Taylor, and Ling Su Wong do not appear in The Princess Diaries movies. This makes Mia’s plight to not lose her friends’ trust that much harder in the movies, but also a lot easier when she regains that trust: Lilly is her only (shown) friend.
Mia does not move to Genovia at the end of The Princess Diaries book
This change may have contributed to the large differences between the movie’s sequel, The Princess Diaries 2: A Royal Engagement and any of the subsequent books. Since many of the books take place throughout Mia’s high school career in New York City, the only feasible way to set the 2004 sequel years later (when Anne Hathaway was 22) would be to have it take place after Mia graduated from high school. While Hathaway did play a 15 year old Mia when she was only 17 (and the movie released when she was 19), it most likely would have been harder to sell a 22-year-old playing an 18-year-old.
Instead, the sequel has Mia having just turned 21 and able to inherit the Genovian throne. Since the movies have Genovia as a monarchy rather than a principality, Grandmère is a Dowager Queen rather than a Princess, which means Mia stands to become Queen of Genovia. However, various ministers scheme to rob Mia of her right, claiming she needs to marry before being eligible for the throne, setting off the plot of the movie: Mia needing to marry someone before
As of August 2004, when the movie was released, only Vols. 1-5 (including Vol. 4.5Â Project Princess) had been released, meaning no Meg Cabot-authored story existed that could feasibly star a 21 or 22-year-old Anne Hathaway as Princess Mia. Rather, all the books released up to that point featured a 14- or 15-year-old Mia.

Michael Moscovitz is a medical entrepreneur, not a famous musician, in the books
Michael is not in a band in Vol. 1: The Princess Diaries. He eventually starts a band in Vol. 4: Princess in Waiting (which was released two years after the film), named Skinner Box, but it disbands after high school.
Rather than break up, which is what happened in order to fuel the plot of The Princess Diaries 2: A Royal Engagement, Mia and Michael remained a happy couple up through Vol. 8: Princess on the Brink, and got back together in Vol. 10: Forever Princess. They married in Vol. 11: Royal Wedding.
The actor who portrayed Michael, Robert Schwartzman, declined to participate in the sequel film because he was touring with his real-life band Rooney at the time of the filming.
Miscellaneous differences
- Lilly’s public access program is named Lilly Tells It Like It Is in the books, not Shut Up and Listen like in the movie.
- Lana and Josh have different names in the books compared to the film: in the books, Lana is Weinberger (not Thomas), while Josh is Richter (not Bryant).
- Josh and Mia go to a beach party in the movie. In the book, they go to the school’s cultural diversity dance.
In the movie, Mia are a corndog. In the book she was a vegetarian, which was a big part of her character.